Multi-zone formation fluid evaluation system and method for use of same

ABSTRACT

A formation fluid evaluation system ( 800 ) interconnected within a tubular string ( 818 ) for operation in a wellbore ( 802 ) having multiple zones ( 806, 808, 810 ). The evaluation system ( 800 ) includes a set of straddle packers ( 820, 822 ) that is operable to sequentially isolate the multiple zones ( 806, 808, 810 ). A test valve ( 824 ) is disposed between the straddle packers ( 820, 822 ). A fluid unloading assembly ( 828 ) is positioned uphole of the straddle packers ( 820, 822 ). The fluid unloading assembly ( 828 ) is operable to draw fluid ( 834 ) from the isolated zone ( 808 ) into the tubular string ( 818 ) through the test valve ( 824 ) in response to the circulation of a drive fluid down the tubular string ( 818 ). A formation evaluation instrument ( 836 ) is disposed within the tubular string ( 818 ) and determines a characteristic of the fluid ( 834 ) received from the isolated zone ( 808 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of co-pending applicationSer. No. 11/811,761 filed on Jun. 11, 2007.

TECHNICAL FIELD OF THE INVENTION

The present invention relates, in general, to testing and evaluation ofsubterranean formation fluids and, in particular, to a single trip,multi-zone formation fluid evaluation system and method for unloadingfluids from each zone prior to evaluating reservoir fluids at reservoirconditions.

BACKGROUND OF THE INVENTION

Without limiting the scope of the present invention, its background isdescribed with reference to testing hydrocarbon formations, as anexample.

It is well known in the subterranean well drilling and completion art toperform tests on formations intersected by a wellbore. Such tests aretypically performed in order to determine geological or other physicalproperties of the formations and the fluids contained therein. Forexample, parameters such as permeability, porosity, fluid resistivity,temperature, pressure and bubble point may be determined. These andother characteristics of the formations and fluids contained therein maybe determined by performing tests before the well is completed.

One type of testing procedure that is commonly performed is to obtain afluid sample from each formation or zone to, among other things,determine the composition of the formation fluids in that zone. In thisprocedure, it is important to obtain a sample of the formation fluidsthat is representative of the fluids as they exist in the reservoir. Ina typical sampling procedure, a sample of the formation fluids may beobtained by lowering a sampling tool having a sampling chamber into thewellbore on a conveyance such as a wireline, slick line, coiled tubing,jointed tubing or the like. When the sampling tool reaches the desireddepth, one or more ports are opened to allow collection of the formationfluids. Once the ports are opened, formation fluids travel through theports and a sample of the formation fluids is collected within thesampling chamber of the sampling tool. After each sample is collected,the sampling tool is withdrawn from the wellbore so that the formationfluid sample may be analyzed. Typically, this procedure must be repeatedfor each zone of interest that is intersected by the wellbore.Accordingly, use of such sampling techniques can be quite time consumingin wellbores having multiple zones.

In addition, it has been found that fluid loss into certain formationsoccurs during the drilling, cementing and completions phases of wellconstruction. In such wells, before a representative fluid sample atreservoir conditions can be obtained, the fluid lost into the formationmust be unloaded or swabbed to initiate the flow of reservoir fluidsinto the wellbore. This swabbing process may take hours for each zonecausing days of delay in wells having multiple zones. Therefore, a needhas arisen for an apparatus and method for evaluating reservoir fluidsfrom multiple zones in a single trip. A need has also arisen for such anapparatus and method that reduce the time spent unloading fluid lostinto the formations during the drilling, cementing and completion phasesof well construction.

SUMMARY OF THE INVENTION

The present invention disclosed herein provides a system and method forevaluating reservoir fluids from multiple zones in a single trip. Inaddition, the system and method of the present invention reduce the timespent unloading fluid lost into the formations during the drilling andcementing phases of well construction.

In one aspect, the present invention is directed to a formation fluidevaluation system that is interconnected within a tubular string foroperation in a wellbore having multiple zones. The evaluation systemincludes a set of straddle packers that isolates one zone of themultiple zones. A test valve is disposed between the straddle packers.The test valve receives fluid from the isolated zone into the interiorof the tubular string. A fluid unloading assembly is positioned upholeof the straddle packers. The fluid unloading assembly is operable todraw fluid from the isolated zone into the tubular string through thetest valve. A formation evaluation instrument is disposed within thetubular string. The formation evaluation instrument determines acharacteristic of the fluid received from the isolated zone. Theevaluation system is operable to sequentially isolate individual zonesof the multiple zones and evaluate fluid received from the individualzones in a single trip.

In one embodiment, the test valve includes a screen element to filterfluids from the zone entering the tubular string. In another embodiment,the fluid unloading assembly includes a pump, such as a jet pump, aprogressive cavity pump, a hydraulic driven piston pump, an electricalsubmersible pump or a syringe pump. In this embodiment, the pump may bedriven by a fluid circulated down the tubular string. In a furtherembodiment, the fluid unloading assembly includes a gas lift valve.

In one embodiment, the formation evaluation instrument is run in thetubular string on a conveyance and passes through the fluid unloadingassembly. In another embodiment, the formation evaluation instrument iscoupled to the tubular string. In one embodiment, the data obtained bythe formation evaluation instrument relative to the characteristic ofthe fluid is transmitted to the surface via a conductor. In anotherembodiment, data obtained by the formation evaluation instrumentrelative to the characteristic of the fluid is transmitted to thesurface via a wireless telemetry device. In yet another embodiment, dataobtained by the formation evaluation instrument relative to thecharacteristic of the fluid is stored in a memory of the formationevaluation instrument.

In another aspect, the present invention is directed to a method ofevaluating multiple zones during a single trip into a wellbore. Themethod involves interconnecting a formation fluid evaluation assemblywithin a tubular string; positioning the formation fluid evaluationassembly in the wellbore proximate one zone of the multiple zones andisolating the zone; unloading fluid from the isolated zone into thetubular string; receiving reservoir fluid from the isolated zone intothe interior of the tubular string; determining a characteristic of thereservoir fluid received from the isolated zone; and performing thepositioning, isolating, unloading, receiving and determining steps foradditional zones of the multiple zones in a single trip.

In a further aspect, the present invention is directed to a formationfluid evaluation system that is interconnected within a tubular stringfor operation in a wellbore having multiple zones. The evaluation systemincludes a set of straddle packers that isolates one zone of themultiple zones. A test valve is disposed between the straddle packers.The test valve receives fluid from the isolated zone into the interiorof the tubular string. A fluid unloading assembly is positioned upholeof the straddle packers. The fluid unloading assembly is operable todraw fluid from the isolated zone into the tubular string through thetest valve in response to a drive fluid circulated down the tubularstring. A formation evaluation instrument is disposed within the tubularstring. The formation evaluation instrument determines a characteristicof the fluid received from the isolated zone. The evaluation system isoperable to sequentially isolate individual zones of the multiple zonesand evaluate fluid received from the individual zones in a single trip.

In another aspect, the present invention is directed to a method ofevaluating multiple zones during a single trip into a wellbore. Themethod involves interconnecting a formation fluid evaluation assemblywithin a tubular string; positioning the formation fluid evaluationassembly in the wellbore proximate one zone of the multiple zones andisolating the zone; pumping a drive fluid down the tubular string;unloading fluid from the isolated zone into the tubular string;receiving reservoir fluid from the isolated zone into the interior ofthe tubular string; determining a characteristic of the reservoir fluidreceived from the isolated zone; and performing the positioning,isolating, unloading, receiving and determining steps for additionalzones of the multiple zones in a single trip.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, includingits features and advantages, reference is now made to the detaileddescription of the invention, taken in conjunction with the accompanyingdrawings in which like numerals identify like parts and in which:

FIG. 1 is a schematic illustration of one embodiment of a formationfluid evaluation system embodying principles of the present invention;

FIG. 2 is a schematic illustration of another embodiment of a formationfluid evaluation system embodying principles of the present invention;

FIG. 3 is a schematic illustration of a further embodiment of aformation fluid evaluation system embodying principles of the presentinvention;

FIG. 4 is a schematic illustration of yet another embodiment of aformation fluid evaluation system embodying principles of the presentinvention;

FIGS. 5A-5B are schematic illustrations of one embodiment of a formationfluid evaluation system embodying principles of the present invention;

FIGS. 6A-6B are schematic illustrations of another embodiment of aformation fluid evaluation system embodying principles of the presentinvention;

FIGS. 7A-7B are schematic illustrations of a further embodiment of aformation fluid evaluation system embodying principles of the presentinvention; and

FIG. 8 is a schematic illustration of yet another embodiment of aformation fluid evaluation system embodying principles of the presentinvention;

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts whichcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention, and do not delimit the scope of theinvention.

Referring initially to FIG. 1, therein is representatively illustrated aformation fluid evaluation system that is generally designated 100 andwhich embodies principles of the present invention. Formation fluidevaluation system 100 is disposed within a wellbore 102 that includescasing 104. Wellbore 102 traverses various earth strata including aplurality of zones of interest such as zones 106, 108, 110 which may beportions of a common formation or reservoir, or one or more of the zonesmay be portions of separate formations or reservoirs. As illustrated,casing 104 includes perforation 112, 114, 116 that correspond inlocation with zones 106, 108, 110, respectively.

Although three zones 106, 108, 110 are depicted in FIG. 1, any number ofzones may be tested with formation fluid evaluation system 100. In fact,one important feature of the present invention is that all of the zonesof interest including zones 106, 108, 110 can be conveniently andrelatively quickly tested in a single trip of formation fluid evaluationsystem 100 into wellbore 102. It should be noted that the term “singletrip” is well known to those skilled in the art, and as used herein, theterm indicates an operation commencing with an initial insertion offormation fluid evaluation system 100 into wellbore 102 and ending witha next subsequent complete retrieval of formation fluid evaluationsystem 100 from wellbore 102.

Formation fluid evaluation system 100 is interconnected within a tubularstring 118 that is preferably made from a plurality of joints of pipethreadably coupled together to form the string. Alternatively, however,tubular string 118 could be formed from other types of tubing includingcoiled tubing or segmented tubing coupled together by other means. Atits lower end, formation fluid evaluation system 100 includes isolationpacker 120 and isolation packer 122 that operate as a set of straddlepackers to isolate the zone of interest to be tested. Packers 120, 122may be similar in design or may vary in setting and releasing technique.For example, packer 122 may be a rotation set packer while packer 120may be a compression set and release packer. In the illustratedembodiment, packers 120, 122 each include a pair of seal elements thatprovide a seal against the interior surface of casing 104. Packers 120,122 are designed such that the integrity of the seals created betweenthe packer elements and casing 104 can be tested prior to operation offormation fluid evaluation system 100. For example, packers 120, 122 maybe set in an unperforated interval of casing 104 and pressure from thesurface may be used to ensure the seals are functioning properly priorto moving to a zone of interest. Alternatively or additionally, apressure reading may be taken between the packer elements by opening asliding sleeve of packers 120, 122 to determine if any leaks exist.

Disposed between packers 120, 122 is a test valve 124. Test valve 124 isused to selectively allow and prevent fluids from entering the interiorof tubing string 104 from the exterior of tubing string 104. Morespecifically, during operation of formation fluid evaluation system 100,test valve 124 is used to selectively allow and prevent fluids fromentering the interior of tubing string 118 from the zone being tested,zone 108 in the illustrated embodiment. Test valve 124 may be a slidingsleeve valve or other suitable fluid flow control device. Test valve 124may also provide a choking functionality to control production intotubing string 118. Alternatively, test valve 124 may simply provide aport to allow fluid to flow therethrough.

As illustrated, formation fluid evaluation system 100 includes anoptional upper packer 126 that may have the same or a different designthan either packers 120, 122 and may preferably be a compression set andrelease packer. In operation, upper packer 126 is positioned uphole ofthe uppermost zone of the multiple zones traversed by wellbore 102. Inthe illustrated example, the uppermost zone is depicted as zone 106. Asexplained in greater detail below, positioning packer 126 uphole of theuppermost zone prevent any power fluid or gas lift fluid, in thoseembodiments using such fluid, from entering zones above the isolatedzone during operation of formation fluid evaluation system 100.

Formation fluid evaluation system 100 also includes a fluid unloadingassembly 128. As illustrated, fluid unloading assembly 128 may bepositioned uphole of upper packer 126. Fluid unloading assembly 128 maybe a pump, such as a fluid operated pump including turbine pumps,hydraulic driven piston pumps or jet pumps, or may be a valve, such as agas lift valve, used to aid in removal of fluid from tubular string 118.Specifically, in operation, fluid unloading assembly 128 is used to drawfluid from the isolated zone, illustrated as zone 108, into tubularstring 118 through test valve 124 and move this fluid to the surface.

In the illustrated embodiment, fluid unloading assembly 128 is beingoperated by a power fluid 130, depicted as arrows with hollowarrowheads, that is circulated down the tubing-casing annulus 132. Powerfluid 130 then enters fluid unloading assembly 128 and passes upwardlythrough a nozzle that is configured to increase a velocity of powerfluid 130, thereby creating a region of reduced pressure about thenozzle exit. As such, fluid unloading assembly 128 operates as a jetpump to carry fluids from zone 108 to the surface in a mixtureconsisting of power fluid 130 and fluid from the zone being tested,which is depicted as arrows 134 having solid arrowheads. The mixture isthen circulated through the tubular string 118 to the surface. It shouldbe noted, however, that various other flow paths may be used in otherconfigurations of fluid unloading assembly 128, without departing fromthe principles of the present invention. Such other configurationsincluding, but not limited to, circulating the power fluid down thetubular string and up the tubing-casing annulus 132 in a mixture of thepower fluid and fluid from the zone.

In the illustrated embodiment, fluid unloading assembly 128 alsoincludes a passageway that allows certain tools, such as a formationevaluation instrument 136, to pass therethrough and receives other toolssecurably and sealing therein. In this embodiment, fluid unloadingassembly 128 may include a nipple of the type which includes an internallanding profile and a seal bore for securing and sealing tools, such asa plug (not pictured), therein. In this configuration, the plug isreceived within fluid unloading assembly 128 to provide a seal thatprevents fluid from passing through the seal bore and forces fluid 134to pass through the jet pump section. This configuration is achievedusing a pair of Y-blocks on the upper and lower ends of fluid unloadingassembly 128 that provides the two fluid paths through fluid unloadingassembly 128.

As illustrated, a formation evaluation instrument 136 has passed throughfluid unloading assembly 128. Formation evaluation instrument 136 isdeployed within tubular string 118 on a conveyance 138 that extends fromthe surface. Conveyance 138 may be a wireline, a slick line, an electricline, a coiled tubing or the like. In operation, formation evaluationinstrument 136 is positioned adjacent or above perforations 114 andincludes a plurality of sensors for determination of one or morecharacteristics of the fluid. For example, formation evaluationinstrument 136 may include sensors for pressure, temperature, flow rate,density, fluid identification, resistivity, capacitance and water cut orany other type of sensor or combination of sensors desired. In addition,formation evaluation instrument 136 may include a flow control device,such as a valve or choke, and one or more sampling chambers forobtaining fluid samples.

If formation evaluation instrument 136 is in the form of a conventionalwireline or slickline conveyed production logging tool, formationevaluation instrument 136 may be retrieved from the well at any time,without also retrieving the remainder of formation fluid evaluationsystem 100. In this configuration, formation evaluation instrument 136could include one or more memory modules which record data for downloadat the surface and may be reinstalled as many times as desired toacquire sufficient data for evaluation of each of the zones of interest.Alternatively, formation evaluation instrument 136 could be conveyed ona conductor cable that provides power and communication to formationevaluation instrument 136 such that real time data from formationevaluation instrument 136 can be sent to the surface. Alternatively oradditionally, formation evaluation instrument 136 may communicate withthe surface via a wire telemetry system.

The characteristics of fluid 134, including changes in thecharacteristics over time, changes in the characteristics in response toinduced stimulus and the like are used to evaluate the properties of thezone, its associated formation or reservoir, the fluid therein and thelike. These evaluations or any portion of them may be performed information evaluation instrument 136 itself or in a computerized systemat the surface. In this case, the computerized system may supply power,receive records and processes data, communicate command and controlsignals, and otherwise facilitates the testing and evaluation of thezones using formation evaluation instrument 136. While such acomputerized system is preferably positioned at a surface location, thecomputerized system or any portion of it could alternatively be locatedelsewhere and communication thereto could be provided via satellitetransmission, Internet transmission or the like.

In operation, formation fluid evaluation system 100 is operable tosequentially isolate individual zones 106, 108, 110 of the multiplezones traversed by wellbore 102 and evaluate fluid received from theindividual zones 106, 108, 110 in a single trip. To achieve this resulttubular string 118 is installed in wellbore 102 such that straddlepackers 120, 122 isolate a portion of annulus 132 adjacent each of thezones 106, 108, 110 when each respective zone is being tested. Asdepicted in FIG. 1, annulus 132 above and below zone 108 is sealed offby the packers 120, 122 straddling perforations 114 formed throughcasing string 104. Preferably, formation fluid evaluation system 100 isused to evaluate the lowermost zone, depicted as zone 110, first thenprogresses uphole, zone by zone, until all zones of interest are tested.Accordingly, FIG. 1 depicts a scenario in which the fluids from zone 110have previously been tested, the fluids from zone 108 are current beingtested and the fluids from zone 106 are yet to be tested.

Once packers 120, 122 are set and zone 108 is isolated, the integrity ofthe seal created between packers 120, 122 and casing string 104 may betested. If it is determined that the seal is good, packer 126 may thenbe set above the uppermost zone 106. If not already deployed, formationevaluation instrument 136 is now run downhole on conveyance 138 to alocation at or near perforations 114 within tubular string 118.Conveyance 138 also deploys a plug that seals within fluid unloadingassembly 128 to prevent flow through the seal bore of fluid unloadingassembly 128 during pumping. Fluid communication between the interior oftubular string 118 and zone 108 via perforations 114 can then beestablished by operating test valve 124 to an open position. As zone 108may have taken on fluids during the drilling and cementing phases ofwell construction, fluid unloading assembly 128 is used to unloadingthis fluid until reservoir fluids are produced from zone 108. This isachieved, in the illustrated embodiment, by circulating power fluid 130through fluid unloading assembly 128 to carry fluids 134 from zone 108to the surface via tubular string 118. After some or all of the fluidbeing produced from zone 108 is reservoir fluid, formation evaluationinstrument 136 is used to determine one or more characteristics of thereservoir fluid, such as the presence of oil in the fluid. Thisdetermination can be made by formation evaluation instrument 136downhole or data relating to the evaluated characteristics may be sentto the surface via a conductor cable associated with conveyance 138,wireless telemetry or by retrieving formation evaluation instrument 136to the surface.

Due to the unique configuration of formation fluid evaluation system100, each of the multiple zones 106, 108, 110 can be evaluated in thismanner by merely repositioning formation fluid evaluation system 100 inwellbore 102 adjacent a respective one of the zones and isolating thatzone, providing a seal uphole of the uppermost zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone.

Even though FIG. 1 depicts a vertical well, it should be noted by oneskilled in the art that the formation fluid evaluation system of thepresent invention is equally well-suited for use in deviated wells,inclined wells or horizontal wells. As such, the use of directionalterms such as above, below, upper, lower, upward, downward and the likeare used in relation to the illustrative embodiments as they aredepicted in the figures, the upward direction being toward the top ofthe corresponding figure and the downward direction being toward thebottom of the corresponding figure. Also, even though FIG. 1 depicts acased wellbore, it should be understood by those skilled in the art thatthe formation fluid evaluation system of the present invention isequally well-suited for use in an open hole environment using, forexample, inflatable packers.

Referring next to FIG. 2, therein is representatively illustrated aformation fluid evaluation system that is generally designated 200 andwhich embodies principles of the present invention. Formation fluidevaluation system 200 is disposed within a wellbore 202 that includescasing 204. Wellbore 202 traverses various earth strata including aplurality of zones of interest such as zones 206, 208, 210. Asillustrated, casing 204 includes perforation 212, 214, 216 thatcorrespond in location with zones 206, 208, 210, respectively.

Formation fluid evaluation system 200 is interconnected within a tubularstring 218. At its lower end, formation fluid evaluation system 200includes isolation packer 220 and isolation packer 222 that operate as aset of straddle packers to isolate the zone of interest to be tested.Disposed between packers 220, 222 is a test valve 224 that is used toallow fluids to enter the interior of tubular string 218 from theexterior of tubular string 218. In the illustrated embodiment, testvalve 224 includes a screen element that filters any solids of apredetermined size out of fluids entering test valve 224.

Formation fluid evaluation system 200 includes an upper packer 226positioned uphole of the uppermost zone 206. Positioned uphole of upperpacker 226 is fluid unloading assembly 228 that is depicted as a fluidoperated pump wherein power fluid 230 circulated through annulus 232drives fluid unloading assembly 228 such that fluid 234 from isolatedzone 208 is drawn into tubular string 218 through test valve 224 and upto the surface. Fluid unloading assembly 228 may include a nipple and aseal bore that allow the passage of formation evaluation instrument 236carried by conveyance 238 therethrough and is sealed by a plug alsocarried by conveyance 238. In this configuration, fluid 234 can bepumped uphole to unload zone 208 until reservoir fluid is produced. Thecharacteristics of the fluid produced from zone 208 can then beevaluated by formation evaluation instrument 236 or other systemsassociate with formation evaluation instrument 236.

Due to the unique configuration of formation fluid evaluation system200, each of the multiple zones 206, 208, 210 can be evaluated in thismanner by merely repositioning formation fluid evaluation system 200 inwellbore 202 adjacent a respective one of the zones and isolating thatzone, providing a seal uphole of the uppermost zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone.

Referring next to FIG. 3, therein is representatively illustrated aformation fluid evaluation system that is generally designated 300 andwhich embodies principles of the present invention. Formation fluidevaluation system 300 is disposed within a wellbore 302 that includescasing 304. Wellbore 302 traverses various earth strata including aplurality of zones of interest such as zones 306, 308, 310. Asillustrated, casing 304 includes perforation 312, 314, 316 thatcorrespond in location with zones 306, 308, 310, respectively.

Formation fluid evaluation system 300 is interconnected within a tubularstring 318. At its lower end, formation fluid evaluation system 300includes isolation packer 320 and isolation packer 322 that operate as aset of straddle packers to isolate the zone of interest to be tested.Disposed between packers 320, 322 is a test valve 324 that is used toallow fluids to enter the interior of tubular string 318 from theexterior of tubular string 318.

Formation fluid evaluation system 300 includes an upper packer 326positioned uphole of the uppermost zone 306. Positioned uphole of upperpacker 326 is fluid unloading assembly 328 that is depicted as ahydraulic pump wherein power fluid, such as a liquid or gas, withinhydraulic lines 330 is circulated downhole to drive a motor within fluidunloading assembly 328 such that fluid 334, from isolated zone 308, isdrawn into tubular string 318 through test valve 324 and up to thesurface. In embodiments using fluid unloading assembly 328 those skilledin the art will recognize that upper packer 326 may be optionallyremoved as loss of power fluid into zones above the isolated zones isnot a concern. In such case, fluid unloading assembly 328 may be locatedproximate packer 320. Fluid unloading assembly 328 may also include anipple and a seal bore that allow the passage of formation evaluationinstrument 336 carried by conveyance 338 therethrough and is sealed by aplug also carried by conveyance 338. In this configuration, fluid 334can be pumped uphole to unload zone 308 until reservoir fluid isproduced. The characteristics of the fluid produced from zone 308 canthen be evaluated by formation evaluation instrument 336 or othersystems associate with formation evaluation instrument 336. If thecharacteristic of the reservoir fluid 334 received from isolated zone308 matches a predetermined characteristic, such as a sufficient oilshow, then formation fluid evaluation system 300 is designed to treatisolated zone 308. Specifically, formation fluid evaluation system 300includes a treatment valve 340 that is used to inject a treatment fluid,such as a fracture fluid with or without propping agents into zone 308.In one implementation, this is achieved by removing formation evaluationinstrument 336 and pumping the treatment fluid down tubular string 318.Following the treatment process, formation evaluation instrument 336 canbe redeployed and fluid from zone 308 may be reevaluated in a mannersimilar to that described above wherein it may be required that fracturefluids are unloaded from zone 308 prior to production of reservoirfluids for evaluation.

Due to the unique configuration of formation fluid evaluation system300, each of the multiple zones 306, 308, 310 can be evaluated andtreated in this manner by merely repositioning formation fluidevaluation system 300 in wellbore 302 adjacent a respective one of thezones and isolating that zone, providing a seal uphole of the uppermostzone, unloading fluid from the isolated zone, receiving reservoir fluidfrom the isolated zone into the interior of the tubular string,determining a characteristic of the reservoir fluid received from theisolated zone and treating the zone if desired.

Referring next to FIG. 4, therein is representatively illustrated aformation fluid evaluation system that is generally designated 400 andwhich embodies principles of the present invention. Formation fluidevaluation system 400 is disposed within a wellbore 402 that includescasing 404. Wellbore 402 traverses various earth strata including aplurality of zones of interest such as zones 406, 408, 410. Asillustrated, casing 404 includes perforation 412, 414, 416 thatcorrespond in location with zones 406, 408, 410, respectively.

Formation fluid evaluation system 400 is interconnected within a tubularstring 418. At its lower end, formation fluid evaluation system 400includes isolation packer 420 and isolation packer 422 that operate as aset of straddle packers to isolate the zone of interest to be tested.Disposed between packers 420, 422 is a test valve 424 that is used toallow fluids to enter the interior of tubular string 418 from theexterior of tubular string 418.

In the illustrated embodiment, formation fluid evaluation system 400includes an optional upper packer 426 positioned uphole of the uppermostzone 406. Positioned uphole of upper packer 426 is fluid unloadingassembly 428 that is depicted as an electrical submersible pump thatreceives power via conductor 430 which drives fluid unloading assembly428 such that fluid 434 from isolated zone 408 is drawn into tubularstring 418 through test valve 424 and up to the surface. As illustrated,conductor 430 is positioned external to tubular string 418 and may beincluded as part of a cable assembly which includes multiple conductors.Those skilled in the art will recognize that conductor 430 couldalternatively be positioned inside of tubular string 418 or integralwith tubular string 418, if, for example, tubular string 418 is acomposite coiled tubing. In addition to providing power to fluidunloading assembly 428, conductor 340 may be used to monitor the pumpperformance, measure pressure differential across the pump and the like.

Also powered by conductor 430 is a formation evaluation instrument 436that is interconnected with tubular string 418. In addition to providingpower to formation evaluation instrument 436, conductor 430 may transmitdata, command signals and the like between formation evaluationinstrument 436 and the surface. In embodiments where conductor 430 onlyprovides power, data and command signals may alternatively betransmitted between formation evaluation instrument 436 and the surfaceby wireless telemetry, such as acoustic, pressure pulse, electromagnetictelemetry and the like. Alternatively, data may be stored in a memory offormation evaluation instrument 436, which may be retrieved to thesurface for download. In operation, fluid 434 is pumped uphole to unloadzone 408 until reservoir fluid is produced. The characteristics of thefluid produced from zone 408 can then be evaluated by formationevaluation instrument 436 or other systems associate with formationevaluation instrument 436.

Due to the unique configuration of formation fluid evaluation system400, each of the multiple zones 406, 408, 410 can be evaluated in thismanner by merely repositioning formation fluid evaluation system 400 inwellbore 402 adjacent a respective one of the zones and isolating thatzone, providing a seal uphole of the uppermost zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone.

Referring next to FIGS. 5A-5B, therein is representatively illustrated aformation fluid evaluation system that is generally designated 500 andwhich embodies principles of the present invention. Unlike thepreviously described formation fluid evaluation systems, formation fluidevaluation system 500 may be disposed in a wellbore that has notpreviously been perforated. As best seen in FIG. 5A, formation fluidevaluation system 500 is being deployed within wellbore 502 thatincludes casing 504. Wellbore 502 traverses various earth strataincluding a plurality of zones of interest such as zones 506, 508, 510.As illustrated, casing 504 includes perforation 514, 516 that correspondin location with zones 508, 510, respectively. Also as illustrated, thecasing adjacent to zone 506 has not been perforated. Preferably,formation fluid evaluation system 500 is used to perforate and evaluatethe lowermost zone, depicted as zone 510, then progresses uphole, zoneby zone, until all zones of interest have been perforated and tested.Accordingly, FIG. 5A depicts a scenario in which zone 510 has beenperforated and evaluated, zone 508 has been perforated but not yetevaluated and zone 506 has not been perforated or evaluated.

Formation fluid evaluation system 500 is interconnected within a tubularstring 518. At its lower end, formation fluid evaluation system 500includes a string of tubing conveyed perforating guns 540 that are usedto form perforations in casing 504 such as perforations 514 adjacent tozone 508. In the illustrated embodiment, perforating guns 540 employ aselect fire system that allows only one or some of the guns to be firedat one time. As such, a plurality of zones can be sequentiallyperforated and evaluated in a single trip using formation fluidevaluation system 500 by aligning the perforating guns with a zone ofinterest, perforating the zone, repositioning the system for isolationand testing of the zone then repeating the process for the other zonesof interest.

As best seen in FIG. 5B, formation fluid evaluation system 500 includesisolation packer 520 and isolation packer 522 that operate as a set ofstraddle packers to isolate the zone of interest to be tested. Disposedbetween packers 520, 522 is a test valve 524 that is used to allowfluids to enter the interior of tubular string 518 from the exterior oftubular string 518. Positioned uphole of packer 520 is fluid unloadingassembly 528 that is depicted as a fluid operated pump wherein powerfluid 530 circulated through annulus 532 drives fluid unloading assembly528 such that fluid 534 from isolated zone 508 is drawn into tubularstring 518 through test valve 524 and up to the surface. Fluid unloadingassembly 528 also includes a nipple and a seal bore that allow thepassage of formation evaluation instrument 536 carried by conveyance 538therethrough and is sealed by a plug also carried by conveyance 538. Inthis configuration, fluid 534 can be pumped uphole to unload zone 508until reservoir fluid is produced. The characteristics of the fluidproduced from zone 508 can then be evaluated by formation evaluationinstrument 536 or other systems associate with formation evaluationinstrument 536.

Due to the unique configuration of formation fluid evaluation system500, each of the multiple zones 506, 508, 510 can be perforated andevaluated in this manner by merely repositioning formation fluidevaluation system 500 in wellbore 502 adjacent a respective one of thezones and perforating the casing, isolating the zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone.

In certain instances, it may be desirable to use tubing conveyedperforating guns in association with one of the previously discussedformation fluid evaluation systems such as systems 100, 200, 300, 400.For example, if it is desired to perforate numerous zones prior toevaluating such zones, it may be desirable to use a formation fluidevaluation system incorporating an upper packer that is operable to beset uphole of the uppermost perforated zone to prevent any of the powerfluid that drives the fluid unloading assembly from entering perforatedzones above the zone being evaluated. Likewise, it may be desirable tosequentially perforate, evaluate, stimulate and reevaluate zones ofinterest by incorporating the tubing conveyed perforating guns 540 intosystem 300 discussed above.

Referring next to FIGS. 6A-6B, therein is representatively illustrated aformation fluid evaluation system that is generally designated 600 andwhich embodies principles of the present invention. As best seen in FIG.6A, formation fluid evaluation system 600 is being deployed withinwellbore 602 that includes casing 604. Wellbore 602 traverses variousearth strata including a plurality of zones of interest such as zones606, 608, 610. As illustrated, casing 604 includes perforation 614, 616that correspond in location with zones 608, 610, respectively. Also asillustrated, the casing adjacent to zone 606 has not been perforated.FIG. 6A depicts a scenario in which zone 610 has been perforated andevaluated, zone 608 has been perforated but not yet evaluated and zone606 has not been perforated or evaluated.

Formation fluid evaluation system 600 is interconnected within a tubularstring 618. At its lower end, formation fluid evaluation system 600includes a valve that selectively allows the passage of wirelineconveyed perforating guns 640 therethrough that are used to formperforations in casing 604 such as perforations 614 adjacent to zone608. In the illustrated embodiment, a plurality of zones can besequentially perforated and evaluated in a single trip using formationfluid evaluation system 600 by deploying the perforating guns throughtubular string 618, perforating the zone, retrieving the perforatingguns, repositioning the system for isolation and testing of the zonethen repeating the process for the other zones of interest.

As best seen in FIG. 6B, formation fluid evaluation system 600 includesisolation packer 620 and isolation packer 622 that operate as a set ofstraddle packers to isolate the zone of interest to be tested. Disposedbetween packers 620, 622 is a test valve 624 that is used to allowfluids to enter the interior of tubular string 618 from the exterior oftubular string 618. Positioned uphole of packer 620 is fluid unloadingassembly 628 that is depicted as a fluid operated pump wherein powerfluid 630 circulated through the wellbore annulus drives fluid unloadingassembly 628 such that fluid 634 from isolated zone 608 is drawn intotubular string 618 through test valve 624 and up to the surface. Fluidunloading assembly 628 may also include a nipple and a seal bore thatallow the passage of formation evaluation instrument 636 carried byconveyance 638 (as well as wireline conveyed perforating guns 640)therethrough and is sealed by a plug also carried by conveyance 638. Inthis configuration, fluid 634 can be pumped uphole to unload zone 608until reservoir fluid is produced. The characteristics of the fluidproduced from zone 608 can then be evaluated by formation evaluationinstrument 636 or other systems associate with formation evaluationinstrument 636.

Due to the unique configuration of formation fluid evaluation system600, each of the multiple zones 606, 608, 610 can be perforated andevaluated in this manner by merely repositioning formation fluidevaluation system 600 in wellbore 602 adjacent a respective one of thezones and perforating the casing, isolating the zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone. It should benoted that formation fluid evaluation systems 100, 200, 300, 400discussed above could be configured to utilize wireline conveyedperforating guns 640 in order to enable sequential perforate andevaluate operations as well as perforate, evaluate, stimulate andreevaluate operations.

Referring next to FIGS. 7A-7B, therein is representatively illustrated aformation fluid evaluation system that is generally designated 700 andwhich embodies principles of the present invention. As best seen in FIG.7A, formation fluid evaluation system 700 is being deployed withinwellbore 702 that includes casing 704. Wellbore 702 traverses variousearth strata including a plurality of zones of interest such as zones706, 708, 710. As illustrated, casing 704 includes perforation 714, 716that correspond in location with zones 708, 710, respectively. Also asillustrated, the casing adjacent to zone 706 has not been perforated.FIG. 7A depicts a scenario in which zone 710 has been perforated andevaluated, zone 708 has been perforated but not yet evaluated and zone706 has not been perforated or evaluated.

Formation fluid evaluation system 700 is interconnected within a tubularstring 718. At its lower end, formation fluid evaluation system 700includes isolation packer 720 and isolation packer 722 that operate as aset of straddle packers to isolate the zone of interest to be perforatedand tested. Disposed between packers 720, 722 is a ported sub 740 thatmay be operated as a hydro-jet perforating gun used to form perforationsin casing 704 such as perforations 714 adjacent to zone 708. In theillustrated embodiment, a plurality of zones can be sequentiallyperforated and evaluated in a single trip using formation fluidevaluation system 700 by deploying the system to a zone of interest,isolating the zone, perforating the zone, testing of the zone thenrepeating the process for the other zones of interest.

Also disposed between packers 720, 722 is a test valve 724 that is usedto allow fluids to enter the interior of tubular string 718 from theexterior of tubular string 718. Positioned uphole of packer 720 is fluidunloading assembly 728 that is depicted as a fluid operated pump whereinpower fluid 730 circulated through the wellbore annulus drives fluidunloading assembly 728 such that fluid 734 from isolated zone 708 isdrawn into tubular string 718 through test valve 724 and up to thesurface. Fluid unloading assembly 728 may also include a nipple and aseal bore that allow the passage of formation evaluation instrument 736carried by conveyance 738 therethrough and is sealed by a plug alsocarried by conveyance 738. In this configuration, fluid 734 can bepumped uphole to unload zone 708 until reservoir fluid is produced. Thecharacteristics of the fluid produced from zone 708 can then beevaluated by formation evaluation instrument 736 or other systemsassociate with formation evaluation instrument 736.

Due to the unique configuration of formation fluid evaluation system700, each of the multiple zones 706, 708, 710 can be perforated andevaluated in this manner by merely repositioning formation fluidevaluation system 700 in wellbore 702 adjacent a respective one of thezones and perforating the casing, isolating the zone, unloading fluidfrom the isolated zone, receiving reservoir fluid from the isolated zoneinto the interior of the tubular string and determining a characteristicof the reservoir fluid received from the isolated zone. It should benoted that formation fluid evaluation systems 100, 200, 300, 400discussed above could be configured to utilize hydro-jet perforating gun740 in order to enable sequential perforate and evaluate operations aswell as perforate, evaluate, stimulate and reevaluate operations.

Referring next to FIG. 8, therein is representatively illustrated aformation fluid evaluation system that is generally designated 800 andwhich embodies principles of the present invention. Formation fluidevaluation system 800 is disposed within a wellbore 802 that includescasing 804. Wellbore 802 traverses various earth strata including aplurality of zones of interest such as zones 806, 808, 810. Asillustrated, casing 804 includes perforation 812, 814, 816 thatcorrespond in location with zones 806, 808, 810, respectively.

Formation fluid evaluation system 800 is interconnected within a tubularstring 818. At its lower end, formation fluid evaluation system 800includes isolation packer 820 and isolation packer 822 that operate as aset of straddle packers to isolate the zone of interest to be tested.Disposed between packers 820, 822 is a test valve 824 that is used toallow fluids to enter the interior of tubular string 818 from theexterior of tubular string 818.

Positioned uphole of packer 820, formation fluid evaluation system 800includes a fluid unloading assembly 828 that is depicted as a fluidoperated pump wherein power fluid 830 circulated through tubular string818 drives fluid unloading assembly 828 such that fluid 834 fromisolated zone 808 is drawn into tubular string 818 through test valve824, into annulus 832 and up to the surface. In embodiments using fluidunloading assembly 828, those skilled in the art will recognize that useof an upper packer, such as upper packer 126 discussed above, isoptional as loss of power fluid into zones above the isolated zone isnot a concern. Fluid unloading assembly 828 may include a nipple and aseal bore that allow the passage of formation evaluation instrument 836carried by conveyance 838 therethrough and is sealed by a plug alsocarried by conveyance 838. Alternatively, formation evaluationinstrument 836 may be tubing conveyed as discussed above with referenceto formation evaluation instrument 436. In this configuration offormation fluid evaluation system 800, fluid 834 can be pumped uphole tounload zone 808 until reservoir fluid is produced. The characteristicsof the fluid produced from zone 808 can then be evaluated by formationevaluation instrument 836 or formation evaluation instrument 836 maysend information to the surface via wired or wireless communication ormay store the information in memory until formation evaluationinstrument 836 is retrieved to the surface.

Due to the unique configuration of formation fluid evaluation system800, each of the multiple zones 806, 808, 810 can be evaluated in thismanner by merely repositioning formation fluid evaluation system 800 inwellbore 802 adjacent a respective one of the zones and isolating thatzone, unloading fluid from the isolated zone, receiving reservoir fluidfrom the isolated zone into the interior of the tubular string anddetermining a characteristic of the reservoir fluid received from theisolated zone.

While this invention has been described with a reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. A formation fluid evaluation system interconnected within a tubularstring for operation in a wellbore having multiple zones, the evaluationsystem comprising: a set of straddle packers that isolates one zone ofthe multiple zones; a test valve disposed between the straddle packers,the test valve receiving fluid from the isolated zone into the interiorof the tubular string; a fluid unloading assembly positioned uphole ofthe straddle packers, the fluid unloading assembly operable to drawfluid from the isolated zone into the tubular string through the testvalve; and a formation evaluation instrument disposed within the tubularstring that determines a characteristic of the fluid received from theisolated zone, wherein the evaluation system is operable to sequentiallyisolate individual zones of the multiple zones and evaluate fluidreceived from the individual zones in a single trip.
 2. The system asrecited in claim 1 wherein the test valve further comprises a screenelement.
 3. The system as recited in claim 1 wherein the fluid unloadingassembly further comprises a pump.
 4. The system as recited in claim 3wherein the pump is selected from a jet pump, a progressive cavity pump,a hydraulic driven piston pump, an electrical submersible pump and asyringe pump.
 5. The system as recited in claim 3 wherein the pump isdriven by a fluid circulated down the tubular string.
 6. The system asrecited in claim 1 wherein the fluid unloading assembly furthercomprises a gas lift valve.
 7. The system as recited in claim 1 whereinthe formation evaluation instrument is run in the tubular string on aconveyance and passes through the fluid unloading assembly.
 8. Thesystem as recited in claim 1 wherein the formation evaluation instrumentis coupled to the tubular string.
 9. The system as recited in claim 1wherein data obtained by the formation evaluation instrument relative tothe characteristic of the fluid is transmitted to the surface via aconductor operably associated with the formation evaluation instrument.10. The system as recited in claim 1 wherein data obtained by theformation evaluation instrument relative to the characteristic of thefluid is transmitted to the surface via a wireless telemetry deviceoperably associated with the formation evaluation instrument.
 11. Thesystem as recited in claim 1 wherein data obtained by the formationevaluation instrument relative to the characteristic of the fluid isstored in a memory of the formation evaluation instrument.
 12. A methodof evaluating multiple zones during a single trip into a wellbore, themethod comprising: interconnecting a formation fluid evaluation assemblywithin a tubular string; positioning the formation fluid evaluationassembly in the wellbore proximate one zone of the multiple zones andisolating the zone; unloading fluid from the isolated zone into thetubular string; receiving reservoir fluid from the isolated zone intothe interior of the tubular string; determining a characteristic of thereservoir fluid received from the isolated zone; and performing thepositioning, isolating, unloading, receiving and determining steps foradditional zones of the multiple zones in a single trip.
 13. The methodas recited in claim 12 further comprising the step of filtering thefluid entering the tubular string from the isolated zone.
 14. The methodas recited in claim 12 wherein the step of unloading fluid from theisolated zone into the tubular string further comprises pumping thefluid to the surface.
 15. The method as recited in claim 14 whereinpumping the fluid to the surface further comprises driving a pump withfluid circulated down the tubular string.
 16. The method as recited inclaim 12 wherein the step of unloading fluid from the isolated zone intothe tubular string further comprises lifting the fluid to the surface.17. The method as recited in claim 12 wherein the step of determining acharacteristic of the reservoir fluid received from the isolated zonefurther comprises obtained data relative to the characteristic of thefluid and transmitting the data to the surface via at least one of wiredand wireless communication.
 18. The method as recited in claim 12wherein the step of determining a characteristic of the reservoir fluidreceived from the isolated zone further comprises obtained data relativeto the characteristic of the fluid and storing the data in a memory. 19.A formation fluid evaluation system interconnected within a tubularstring for operation in a wellbore having multiple zones, the evaluationsystem comprising: a set of straddle packers that isolates one zone ofthe multiple zones; a test valve disposed between the straddle packers,the test valve receiving fluid from the isolated zone into the interiorof the tubular string; a fluid unloading assembly positioned uphole ofthe straddle packers, the fluid unloading assembly operable to drawfluid from the isolated zone into the tubular string through the testvalve in response to a drive fluid circulated down the tubular string;and a formation evaluation instrument disposed within the tubular stringthat determines a characteristic of the fluid received from the isolatedzone, wherein the evaluation system is operable to sequentially isolateindividual zones of the multiple zones and evaluate fluid received fromthe individual zones in a single trip.
 20. A method of evaluatingmultiple zones during a single trip into a wellbore, the methodcomprising: interconnecting a formation fluid evaluation assembly withina tubular string; positioning the formation fluid evaluation assembly inthe wellbore proximate one zone of the multiple zones and isolating thezone; pumping a drive fluid down the tubular string; unloading fluidfrom the isolated zone into the tubular string; receiving reservoirfluid from the isolated zone into the interior of the tubular string;determining a characteristic of the reservoir fluid received from theisolated zone; and repeating the positioning, pumping, unloading,receiving and determining steps for additional zones of the multiplezones in a single trip.